1. Field of the Invention
The present invention relates to an electromagnetic interference eliminating apparatus. In particular, this invention relates to an electromagnetic interference eliminating apparatus that eliminates the common mode voltage noise and the differential mode voltage noise generated from the electromagnetic interference (EMI).
2. Description of the Related Art
In a circuit, the sudden current or voltage change in the rectifier diode, the filtering capacitor and the bead will generate EMI. High order harmonic noise also exists in the circuit. If the EMI is not eliminated, the loading equipments or the circuit may be damaged. Therefore, in some countries there are safety rules concerning EMI.
As the operating frequency of the circuit becomes higher, the EMI problem also becomes more serious. Therefore, an EMI filter is fitted to the circuit. The EMI filter eliminates the common mode voltage noise and the differential mode voltage noise to meet the safety standards.
The traditional EMI eliminating method is to increase the capacitance, increase the quantity of the capacitors, or connect beads in serial so as to eliminate the common mode voltage noise or the differential mode voltage noise generated from the EMI.
However, the filter for eliminating the common mode voltage noise or the differential mode voltage noise generated from the EMI usually uses the inductor as the dominate components. The application frequency range is very narrow so that its effect is poor. Furthermore, it still cannot eliminate the high frequency harmonics. When it processes the EMI, the important signal may be attenuated and deformed.